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[pacman366]

I was having similar issues until i soldered the diode directly to jd2.2 as apposed soldering it to pin 6 on the front panel. i also soldered a 330ohm resistor between jd2.4 and 2.7. Not sure of what fixed the random e79s, it could have also had something to do with the xboxs pbc and the way it was remounting to the chassis , when ever i applied pressure to the board it would immediately e79 and flash the lower right hand corner red light on the rf panel while booted to xbreboot .

[FrostyTheSnowman]

QUOTE(pipeme @ Dec 22 2009, 07:19 AM)

Hi guys

My jtagged system will randomly fail on power up with no error code, it just sits there.  if I power off then on again, I may get an e79 error, or nothing again, and other times it will boot up fine and let me do whatever.

I can't get it to boot at all when using my controller to power on the xbox, I have to use th epower button on the console itself.

When I flashed my NAND I only used the kv file as when I used both the kv and config files it failed.

What could the cause be?

Bad blocks?
JTAG wiring?
lack of config file?

Thanks

Nope, actually this issue you are describing is directly related to solder-joint issues under your GPU.

I had the same problem with my Xenon (random E79 errors) and after some digging and research (trying multiple JTAG wiring setups - 2 wire diode method, 2 wire resistor method and 3 wire resistor method, different diodes/resistors, etc) I discovered that the issue was being caused by the GPU not having proper contact with the motherboard. (which causes the JTAG points that are traced to the bottom of the GPU to disconnect randomly, causing the JTAG hack to not function, resulting in E79 errors)

After reflowing the GPU with a heatgun everything worked perfectly, no more random E79 errors.

[pipeme]

QUOTE(pacman366 @ Dec 23 2009, 05:31 PM)

My issues seemed to have stopped after re-installing the diode and installing the 330ohm resistor. im not sure wich fixed the issue if any at all, because i performed both simultaneously in one sitting. i have not had an e79 since, and iv booted my xbox roughly 20-30 times since i attempted the fix, not one e79. Before the fix, roughly one in 3 boot up attempts would result in a e79.

I'll try this first, heat gunning the GPU stuff sounds daunting!

What wattage was the 330 resitor?  1/2 watt or a full 1?

Also with your diode, did you point the black line to J2D2 or kept it toward pin 6?

[pacman366]

I used a 1/2w , from what i understand it does not matter, its a measurement of maximum heat generated by current allotted for the resistor to operate under. as for the diode, through your soldering it directly to JD2.2, insure the black line marked on the diode is facing the direction of pin 6 on the front panel.

[rastaman108037]

From what I understand, E79 is caused by an error with the JTAG/gpu. There's a 99% chance you need to fix the JTAG points if this happened. The switching diode should work just fine (works on my xenon).

You may want to dump your NAND and compare it with the XBR image. You may have some differences.

[pipeme]

During my r6t3 resistor removal, I decided to resolder my IR receiver point 6 wire.  To me it looked good, but I said what the heck.  Looks like this actually fixed it.  I can now start the xbox using my controller and it has booted up each time.  Funny thing is, my new solder job looks worse than the first time! Go figure.

Thank you to all that made their suggestions.